Nowadays, many portable electronic devices such as handheld computers, personal digital assistants (PDAs) and mobile telecommunication devices such as radio telephones comprise colour displays, often in the form of liquid crystal displays (LCDs). Such colour displays are becoming commonplace and are likely to supersede black and white and grey-scale displays.
However, one problem with the colour displays is that they generally drain a higher current from the battery than the black and white and grey-scale counterparts, thus reducing the battery life.
Another problem associated with colour displays is concerned with the illumination of the displays. Unlike the black and white and grey-scale displays, the colour displays can only be viewed clearly and comfortably with the display backlight switched on. In the absence of illumination provided by the backlight, the display can be difficult to read and the displayed colours do not look appealing. Furthermore, illumination of colour displays is not only required in dark environments, but in normal daylight conditions.
On some portable electronic devices it is possible for the user to set a backlight timeout period or a backlight illumination duration. Therefore, since colour displays require backlight illumination for comfortable and appealing viewing, the user can set the backlight illumination duration or backlight timeout period to a duration that is sufficient to view the information being displayed.
However, for many portable electronic devices, such as radio telephones, it is not possible for the user to set the backlight timeout period or backlight illumination duration. Instead, the backlight timeout period or backlight illumination duration will be configured upon manufacture of the device and will be applied to all backlight on states of the display irrespective of the information being displayed. This is usually done for design simplicity and consistency. Because of the variation in type and volume of information that may be displayed, the predetermined backlight illumination duration corresponds to an average time required to view the displayed information. Consequently, the illumination duration is often unnecessarily long when viewing colour displays comprising minimal information, such as idle screens or short text messages, resulting in unnecessary and undesirable reduction in battery life.
One attempt to address this problem involves incorporating a count module in portable electronic devices that counts the number of characters to be displayed. An illumination control module adjusts the duration of the illumination provided by the backlight according to the number of characters by referring to an illumination period look-up table. For example, if between 1 and 100 characters are to be displayed, illumination may be provided by the backlight for 30 seconds. If between 101 and 150 characters are to be displayed, illumination may be provided by the backlight for 45 seconds. The look-up table also comprises pre-set illumination periods that are dependent on the application in use on the portable electronic device. For example, if the device is being used for a telephone call, the backlight illumination period may be 30 seconds. If the device is being used for a memo application, the backlight illumination period may be 45 seconds. The backlight illumination period may also be pre-set according to both the number of characters displayed and the application in use.
Although the aforementioned character count dependent and/or application dependent illumination period schemes reduce some unnecessary battery usage, these schemes are not sensitive to the importance or otherwise of the information being displayed. For example, if the illumination period depends on the number of displayed characters and a short, but important message is displayed, such as a missed call message, the display may only be illuminated for a short period resulting in the missed call message being overlooked. Similarly, if the device is in use for an application for which the pre-set illumination period is relatively short, and important information is displayed, such as an incoming message icon, the illumination period may be insufficient to attract a user's attention to the important information. Hence, the backlight illumination periods of these schemes do not take into account the context of the information displayed.
Another deficiency in the illumination of displays of portable electronic devices such as radio telephones is that once backlight illumination is required, all of the illumination elements employed for illumination, which are often light emitting diodes (LEDs), are activated and the entire display is illuminated, even if there is only a small amount of information, such as an icon or a short text message, to be viewed. This also results in unnecessary and undesirable reduction in battery life, particularly with a current trend towards larger display screens in portable electronic devices.
Accordingly, there exists a need for one or more backlight illumination methods for illuminating the displays of portable electronic devices that are considerate of the type and volume of information being displayed and which conserve battery life.
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